The present invention claims priority under 35 U.S.C. xc2xa7 119 of German Patent Application No. 198 31 277.6, filed on Jul. 13, 1998, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The invention relates to a process and device for packaging a material web roll, and more particularly to a process and device for holding a material web roll wherein at least the beginning of a packaging web is held against the circumference of the material web roll.
2. Discussion of Background Information
The invention is described below using a paper web roll as an example of a material web roll. In principle, however, it can also be used with other material web rolls, for example, with rolls of films of plastic or metal or with rolls of endless cardboard.
Material web rolls to be packaged are of considerable size, having a diameter generally in the range of about 500 to 2,100 mm. Roll width is customarily 500 to 3,800 mm or even greater. Material web rolls of this type are created, for example, in the production of paper or textiles. To enable the material web rolls to be transported from their production site, such as a paper mill, to the site where they will be used, such as a printing plant, they must be wrapped in a packaging web for protection. The packaging web provides protection against damage and is also intended to minimize the effect of environmental factors such as atmospheric humidity.
Bonding packaging web with the circumference of a material web roll by applying an adhesive substance between the packaging web and the material web roll is known. This procedure, however, may result in damage to the material web roll. Also, the outer layer of the material web roll is often damaged during unpacking of the material web roll. Further, underlying layers of the material web are also damaged during unpacking.
Therefore, to avoid adhesive bonding, the beginning of the packaging roll is wound around the circumference of the material web roll until the next layer of the packaging web holds the beginning firmly with sufficient tension. When the material web roll is then rotated further, the holding device can be stopped. The packaging is considered xe2x80x9cself-locking,xe2x80x9d i.e., further layers of packaging web may be applied without the beginning of the packaging web slipping on the circumference of the material web roll, because this beginning is held firmly by the packaging web itself.
However, this procedure is relatively costly. The necessary winding and holding devices are relatively complicated and require additional floor space. Furthermore, this device increases the number of components in which failures can occur. Consequently, there is an increased risk of interruption of the packaging process.
The present invention provides a process and device for packaging a material web roll. The device of the invention includes a packaging web dispenser, a holding device adapted to hold at least the beginning of a packaging web against the circumference of the material web roll, and a rotary drive for rotatably driving the material web roll. The holding device includes a pressure-sensitive adhesive dispenser and a pressing device.
According to one feature of the invention, the pressure-sensitive adhesive dispenser is a spray device. The pressing device may include a nip between the material web roll and a driven roller. Further, the driven roller may be adapted to support the material web roll thereon.
The packaging web dispenser may be adapted to dispense the packaging web at a predetermined angle to the longitudinal axis of the material web roll.
The process for packaging a material web roll according to the present invention includes holding at least the beginning of a packaging web against the circumference of the material web roll, rotating the material web roll, and detachably bonding the packaging web to the circumference of the material web roll with the aid of a pressure-sensitive adhesive.
The process may further include applying the pressure-sensitive adhesive to the packaging web. Additionally, the process may include feeding the packaging web through at least one nip between the material web roll and a driven roller. Also, the material web roll may lie on the driven roller.
Further, the process may include successively winding a plurality of layers of the packaging web around the material web roll, and nondetachably binding each successive packaging web layer to the preceding wound packaging layer, using an adhesive that is not pressure-sensitive. The winding may be performed in a spiral.
The process may yet further include spraying the pressure-sensitive adhesive onto at least one of the packaging web and the material web roll.
The present invention packages a material web roll without damaging the surface thereof. The method of the invention does so by detachably bonding the packaging web with the circumference of the material web roll with the aid of a pressure-sensitive adhesive.
A pressure-sensitive adhesive that is suitable for this application is available, for example, under the product name xe2x80x9cJOWATEXxe2x80x9d from Jowat Lobers und Frank GmbH and Co. KG, Wittekindstrasse 19, D-32709 Detmold, Germany. The pressure-sensitive adhesive ensures a bond between at least the beginning of the packaging web, and the circumference of the material web roll. The pressure-sensitive adhesive has a bonding strength of 8 g/cm2, more preferably 70 g/cm2, and most preferably 75 g/cm2. This bond is sufficiently stable to hold the beginning of the packaging web firmly on the circumference of the material web roll until a subsequent layer or band of the packaging web can exert additional forces on the layer forming the beginning, which takes place in a relatively short period of time (i.e., slightly more than one complete rotation of the material web roll). When the material web roll is to be unpacked, the wrapping formed by the packaging web is customarily destroyed. In contrast to previously known gluing processes, the packaging web can be peeled from the material web roll without leaving a residue. In addition to the material web roll being undamaged on its circumference, the disposal of the packaging is also improved. A homogeneous material is obtained that consists solely of the packaging web and contains no constituents of the material web roll. The packaging web customarily consists of packing paper. This packing paper is then unmixed with xe2x80x9cwhitexe2x80x9d paper of the material web roll or other materials that have been wound on the material web roll, which facilitates recycling of the packaging web material.
According to a certain feature of the invention, the pressure-sensitive adhesive is applied to the packaging web. The pressure-sensitive adhesive is applied shortly before the packaging web is bonded to the material web roll so that the pressure-sensitive adhesive first bonds with the packaging web and makes only its surface tacky. When the packaging web is peeled from the circumference of the material web roll, the pressure-sensitive adhesive remains on the packaging web and not on the circumference of the material web roll. The circumference of the material web roll remains clean and virtually free of residues.
According to another feature of the invention, the packaging web is fed through at least one nip between the material web roll and a driven roller. This nip presses the packaging web, which has been made tacky, against the circumference of the roller, which causes the packaging web to be bonded to the circumference of the material web roll with sufficient strength, although pressure-sensitive adhesives have lower holding power than hot or cold glue used previously in the art. Since the roller is driven, the packaging web is also driven by the roller, so that the bonding site between the beginning of the packaging web and the circumference of the material web roll is not stressed excessively by tensile forces. The packaging web is therefore xe2x80x9cpulled along,xe2x80x9d at least at the beginning, not only by the rotation of the material web roll but also by the driven roller, which acts on the packaging web.
It is also advantageous for the material web roll to lie on the driven roller. The weight of the material web roll is then used to produce a certain pressure acting in the nip, making further measures unnecessary.
It is further advantageous for several layers of the packaging web to be wound around the material web roll, whereby each respective further exterior layer is nondetachably bonded to the layer or band below it, with a different adhesive. The term xe2x80x9cnondetachablyxe2x80x9d refers to the situation that when the bond produced with this adhesive is separated, there is a risk of damaging at least one layer of the packaging web. In the present invention, two different adhesives may be used during packaging, namely, a first, pressure-sensitive, adhesive to produce the detachable xe2x80x9cinitial gluing,xe2x80x9d and a second, xe2x80x9cnormal,xe2x80x9d adhesive to produce the packaging about the body of the web roll. However, this arrangement saves the relatively complicated winding process for the beginning of the packaging web, so that any additional effort is readily justified. Because the layers of the packaging web are bonded permanently with one another, a very stable packaging is obtained, whereby it does not matter that the beginning of the packaging web has only a relatively weak adhesive bond to the circumference of the material web roll.
Advantageously, the packaging web may be wound around the material web roll in a spiral. In other words, the longitudinal edge of the packaging web has a predetermined angle to the longitudinal axis of the material web roll. This type of packaging process is known for example from German Patent Document No. DE 195 35 746 C2. With this type of packaging, it is virtually impossible, at a reasonable cost, to wind the beginning of the packaging web around the circumference of the material web roll until the next layer grips, to hold the beginning firmly. Therefore, the use of a pressure-sensitive adhesive is a good alternative if it is desired to avoid the beginning of the packaging web being permanently glued to the circumference of the material web roll.
Preferably, the pressure-sensitive adhesive is sprayed onto the packaging web. Spraying is advantageous in that the pressure-sensitive adhesive already acquires a relatively intensive contact with the air and thus with atmospheric oxygen during the application. Therefore, spraying ensures that the pressure-sensitive adhesive exhibits a high adhesiveness relatively fast, so that a sufficiently stable adhesive bond between the beginning of the packaging web and the circumference of the material web roll can be achieved in only a short time after the pressure-sensitive adhesive has been applied to the packaging web.
The holding device of the present invention includes a pressure-sensitive adhesive dispenser and a pressing device.
As with the process of the present invention, the holding device not only ensures that the pressure-sensitive adhesive is applied to the packaging web, and also ensures that the pressing device creates a sufficiently stable bond between the beginning of the packaging web and the circumference of the material web roll. When the pressing device has pressed the beginning of the packaging web against the circumference of the material web roll, a bond exists between the material web roll and the packaging web that is sufficient to wind the beginning of the packaging web far enough around the material web roll, because of the pressure-sensitive adhesive. This bond does not need to be durable or extremely stable; it merely replaces previously known holding methods.
The pressure-sensitive adhesive dispenser is preferably designed as a spray device. This pressure-sensitive adhesive may be sufficiently oxidized during the application to develop its adhesiveness.
The pressing device is preferably formed by a nip between the material web roll and a driven roller. After the area between the material web roll and the packaging web has been made tacky and has traveled through the nip, the driven roller of this nip serves to convey the packaging web further. The stress on the bonding site between the material web roll and the packaging web is correspondingly minimized.
Preferably, the material web roll lies on the roller. The weight of the material web roll is therefore used to press downward on the roller.
It is preferable for the packaging web dispenser to dispense the packaging web at a predetermined angle to the longitudinal axis of the material web roll. In this arrangement, the packaging web can be wound around the material web roll in a spiral. This is advantageous in that a single packaging web is sufficient, for example, a packaging web having a width of 500 mm, even with material web rolls having varied widths. Correspondingly, this arrangement facilitates the maintenance of the supply of the packaging web considerably. It is only necessary to keep packaging rolls of the same size (e.g., 500 mm wide), on hand. Normally, packaging in a spiral makes it more difficult to bond the beginning of the packaging web with the material web roll if permanent gluing is not used. However, the use of pressure-sensitive adhesive solves this problem.